Low Molecular Weight Priority Polycyclic Aromatic Hydrocarbons Research Articles

Occurrence, source modeling, influencing factors and exposure assessment of polycyclic aromatic hydrocarbons in water sources: A mega-study from mainland China

This study investigates the composition and distribution of 16 priority polycyclic aromatic hydrocarbons (PAHs) in 70 water samples collected from centralized drinking water sources (CDWSs) across 30 provinces (cities) in mainland China. Additionally, water quality and socio-economic data were collected to determine the influencing factors. The study discovered that the total concentrations of 16 priority PAHs (Σ16PAHs) varied from 0.17 to 176.71 ng/L (mean: 56.49 ± 38.58 ng/L). Lakes and reservoirs had significantly higher concentrations of PAHs than groundwater. The primary pollutants were low-molecular-weight (LMW) PAHs, such as phenanthrene, naphthalene, and fluorene. There was a strong correlation between LMW PAHs and Σ16PAHs (p < 0.05). The mean Σ16PAHs in the seven geo-environmental zones were ranked as follows, under the comprehensive influence of emission density, natural, and social environmental factors: Northwest China (78.42 ± 66.96 ng/L) > Northeast China (73.70 ± 33.23 ng/L) > East China (64.35 ± 45.66 ng/L) > North China (50.95 ± 31.87 ng/L) > Southwest China (44.05 ± 32.56 ng/L) > Central China (41.68 ± 19.44 ng/L) > Southern China (40.99 ± 16.54 ng/L). The source modeling analysis revealed that the majority of PAHs came from chemical production and metal smelting (42.36%), as well as from the combustion of coal, wood, and biomass (34.17%), and other mixed sources. In addition, the study found a strong correlation between water quality and socio-economic factors with concentrations of PAHs, indicating that these factors may contribute to the re-enrichment, transport, and transformation of PAHs in overlying water to varying degrees. The mean incremental lifetime cancer risk (ILCR) was lower than the risk threshold. These findings provide scientific references for managing hazardous substances in the aquatic environment.

Evaluation of Appropriate Conditions for Efficient Simultaneous Determination of US EPA and EU Priority Polycyclic Aromatic Hydrocarbons in Various Food Categories and Assessment of Their Consumption Risk.

The QuEChERS (quick, easy, cheap, effective, rugged and safe) conditions were optimized for efficient determination of the U.S. Environmental Protection Agency (US EPA) and European Union (EU) priority polycyclic aromatic hydrocarbons (PAHs) for the categories of grains, tuber & starchy vegetables, soy beans and products, fish & seafood, and poultry & meat, including raw materials and their corresponding products. The PAHs were analyzed using ultrahigh-performance liquid chromatography with temperature-controlled fluorescence detection and gas chromatography with tandem mass spectrometry. The established conditions had good accuracy, repeatability, and precision. Environmental pollution and processing methods influence the level of PAHs in samples. The low molecular weight PAHs were present in all raw materials, and processing increased high and low molecular weight PAHs in the products. The excess cancer risk for consumption of PAHs in cooked samples was mostly acceptable; a small number of samples might be of slight concern in certain age groups.

Molecular distribution, sources and potential health risks of fine particulate-bound polycyclic aromatic hydrocarbons during high pollution episodes in a subtropical urban city

Abundance of fine particulate-bound 16 priority polycyclic aromatic hydrocarbons (PAHs) was investigated to ascertain its sources and potential carcinogenic health risks in Varanasi, India. The city represents a typical urban settlement of South Asia having particulate exposure manyfold higher than standard with reports of pollution induced mortalities and morbidities. Fine particulates (PM2.5) were monitored from October 2019 to May 2020, with 32% of monitoring days accounting ≥100 μgm−3 of PM2.5 concentration, frequently from November to January (99% of monitoring days). The concentration of 16 priority PAHs varied from 24.1 to 44.6 ngm−3 (mean: 33.1 ± 3.2 ngm−3) without much seasonal deviations. Both low (LMW, 56%) and high molecular weight (HMW, 44%) PAHs were abundant, with Fluoranthene (3.9 ± 0.4ngm−3) and Fluorene (3.5 ± 0.3ngm−3) emerged as most dominating PAHs. Concentration of Benzo(a)pyrene (B(a)P, 0.5 ± 0.1ngm−3) was lower than the national standard as it contributed 13% of total PAHs mass. Diagnostic ratios of PAH isomers indicate predominance of pyrogenic sources including emissions from biomass burning, and both from diesel and petrol-driven vehicles. Source apportionment using receptor model revealed similar observation of major PAHs contribution from biomass burning and fuel combustion (54% of source contribution) followed by coal combustion for residential heating and cooking purposes (44%). Potential toxicity of B[a]P equivalence ranged from 0.003 to 1.365 with cumulative toxicity of 2.13ngm−3. Among the PAH species, dibenzo[h]anthracene contributed maximum toxicity followed by B[a]P, together accounting 86% of PAH induced carcinogenicity. Incremental risk of developing cancer through lifetime exposure (ILCR) of PAHs was higher in children (3.3 × 10−4) with 56% contribution from LMW PAHs, primarily through ingestion and dermal contact. Adults in contrast, were more exposed to inhale airborne PAHs with cumulative ILCR of 2.2 × 10−4. However, ILCR to PM2.5 exposure is probably underestimated considering unaccounted metal abundance thus, require source-specific control measures.

Pollution level and health risk assessment of polycyclic aromatic hydrocarbons in marine fish from two coastal regions, the South China Sea

Marine fishes are consumed in large quantities by humans as nutritious food. However, the intake of fish polluted by chemicals may pose a severe threat to human health. This study measured the concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) in the muscles of 22 species of marine fish from two coastal regions, i.e., Tanmen and Zhuhai, identified the source of PAHs, and assessed the human health risk by dietary exposure. Total PAH (Σ16PAHs) levels in Tanmen and Zhuhai fish were in the range of 24.29–684.83 ng g−1 dry weight (dw) and 13.74–42.59 ng g−1 dw, averaging 161.46 ng g−1 dw and 31.21 ng g−1 dw, respectively. Compared with other regions in the world, PAH concentrations in Tanmen fish were at median levels, and Zhuhai fish were at low levels. Low molecular weight PAHs (with 2- and 3-rings) were the predominant compounds detected. Molecular diagnostic ratios suggested that PAHs in Tanmen mainly originated from petrogenic sources such as vessel operations or tanker accidents, while Zhuhai fish were mainly polluted by pyrolytic sources such as combustion of coal and wood. The human health risk assessment results indicated that the risk of PAH intake via fish consumption from Zhuhai was negligible, while five species from Tanmen may pose potential health risks to local residents.

Distribution and the use of diagnostic ratios for source investigation in urban soils of the Yenagoa City, Bayelsa State, Nigeria

Yenagoa is a non-industrialized city. This work aims to investigate the distribution, content and source of the sixteen United State Environmental Protection Agency (USEPA) priority polycyclic aromatic hydrocarbons (PAHs) in urban soils of the Yenagoa, Bayelsa State, Nigeria. The PAH concentrations in the urban soil samples were performed using GC–MS method. The Swali market axis of the city had the highest concentration (∑PAHs). The burden of low molecular weight (LMW) PAHs follows a decreasing order: Phenanthrene > acenaphthene>cenaphthylene>naphthalene> anthracene>fluorine and while the burden of high molecular weight (HMW) PAHs follows the decreasing order: Pyrene> Dibenzo (a,h) anthracene > indeno [1,2,3-cd] pyrene (InP> Chrysene> Fluoranthene> Benzo(a)anthracene> Benzo(k)fluoranthene> Benzo(b)fluoranthene. PAH fingerprint ratios for determining both petrogenic and pyrogenic (pyrolytic) PAH accumulation was employed. The Ph/An ratio for the soil samples were 2.49, 3.47, 0.613, 1.59, 1.99 and 2.44 respectively. This may be indicative of pyrogenic (pyrolytic) origin. Ind(1,2,3-cd)P and DbahA were high in the soils, this may indicate a major concern for carcinogenic risk and demands an urgent attention from policy makers and the government.

Spatial-temporal variations and transport process of polycyclic aromatic hydrocarbons in Poyang Lake: Implication for dry–wet cycle impacts

The dry-wet cycles of the lake-catchment system may affect the spatial-temporal variations and transport of specific volatile organic compounds. In this study, we analyzed 16 priority polycyclic aromatic hydrocarbons (PAHs) in water, suspended particulate matter (SPM), air, soil and sediment in the Poyang Lake, which is the largest freshwater lake in Southeast China. The samples were collected from intertidal zone of the Poyang Lake, in both the dry and wet seasons, corresponding to the exposure and submersion periods, respectively. Concentrations of target PAHs in air, water, SPM and sediments were 0.8–13.5 ng/m3, 5.1–62.0 ng/l, 117–4651 ng/g and 16.4–775 ng/g, respectively. Concentrations of PAHs in sediments were found to be significantly related to total organic carbon and water content (p < 0.01). Compared to the sediment samples, the low molecular weight (LMW) PAHs (2–3 rings) accounted for greater proportions in water, SPM and air. Results suggest that the occurrences of PAH species are affected by their lipophilic properties. Molecular diagnostic ratios of PAH isomers in multimedium indicated that PAH presence in the Poyang Lake were attributed to both pyrogenic and petrogenic sources, and source contributions in different medium were shown to vary. Sediment-water and soil-air exchanges showed that the sediment plays a role of secondary emission sources for most LMW PAHs, and some high molecular weight PAHs (e.g., BghiP, IcdP and DahA) had different transmission directions in the alternate process of exposure and submersion. These findings provide a better understand of migration mechanism among the air, water body (including water and SPM) and sediment PAHs driven by dry-wet cycles.

Health risk assessment of polycyclic aromatic hydrocarbons via dietary intake of leafy vegetables

ABSTRACT The 16 US-EPA priority polycyclic aromatic hydrocarbons (PAHs) can reach to potentially hazardous levels in leafy vegetables as studies suggest. In this study, the 16 PAHs were quantified in samples of lettuce, cabbage, celery and spinach collected from Tehran central fruit and vegetable market in summer and winter using gas chromatography mass spectrometry (GC-MS). The results indicated the dominance of low molecular weight PAHs (LPAHs) in all vegetables. With respect to total mean concentration, the vegetables were ordered as follows: lettuce (51.61 µg/kg) > cabbage (28.13 µg/kg)> spinach (24.85 µg/kg) > celery (9.98 µg/kg). Isomeric ratios and principal component analysis (PCA) suggested diesel and gasoline vehicles, petroleum and coke ovens as the sources of pollution. No statistically significant difference was found between summer and winter regarding the total mean concentrations of 16 PAHs in the vegetables. The estimated combined lifetime average daily dose (LADD) was 3.36E-6 (mg/kg/day) and the estimated excess lifetime cancer risk (ELCR) upper confidence limit (P95%), using Monte Carlo Simulation (MCS) in Oracle Crystal Ball software, was 3.88E-5, indicating low cancer risk. Assessment of target hazard quotient (HQ) showed no possible adverse health effect. Sensitivity analysis showed exposure duration, Benzo[a]pyrene equivalent concentration (BaPeq) and body weight (BW) as the most influential parameters.

Occurrences of polycyclic aromatic hydrocarbon from Adayar and Cooum Riverine Sediment in Chennai city, India

In Chennai city, India, the industrial outfalls, port activities and anthropogenic activities dump a significant amount of waste in the riverine belts of two major rivers, viz. Cooum and Adayar. Hence, this paper aims to study the occurrences and sources of 16 priority polycyclic aromatic hydrocarbons (PAHs) enlisted in United States Environmental protection Agency. Gas chromatography–mass spectrometry analysis showed that total PAHs in surface riverine sediment ranged from 136 to 2063 ng/g (Average ± SD, 654 ± 801 ng/g dw) for Cooum and 105–1710 ng/g (Average ± SD, 380 ± 593 ng/g) for Adayar. Generally, high molecular weight PAHs were higher than low molecular weight PAHs. A prevalence of high molecular weight carcinogenic PAHs was suspected due to incomplete combustion. Principal component analysis and diagnostic ratios revealed that emission sources were from pyrogenic (vehicular emissions), as well as significant contribution was from petrogenic inputs. Principal component analysis also revealed that for both riverine sediments in PC1 65% of high molecular weight compounds were from informal e-waste recycling area and industrial corridor possibly associated with industrial effluents and recycling activities. The ecological risk assessment using probable effect level estimation suggested that PAHs are likely to cause no adverse effect or slightly adverse in all the sites of Cooum and Adayar excluding in residential sites (CR-03, AD-02) and e-waste site (CR-16) which were under heavy and moderate ecological impact. Further toxic equivalent factor also showed that residential site (AD-02) was affected by moderate level loading of benzo[a]pyrene.

Polycyclic aromatic hydrocarbons in sediments and marine organisms: Implications of anthropogenic effects on the coastal environment

Intensive human activities aggravate environmental pollution, particularly in the coastal environment. Sixteen priority polycyclic aromatic hydrocarbons (PAHs) were determined in the sediments and marine species from Zhanjiang Harbor, a large harbor in China. The total PAH concentrations ranged from 151 to 453 ng/g dry weight (dw) in sediments and from 86.7 to 256 ng/g wet weight (ww) in organism tissues. High levels of PAHs occurred in the sample sites next to the estuary. A decrease in PAH levels was observed in comparison to the previous survey prior to 2012. Fish exhibited lower lipid weight normalized PAH concentrations than the other species, which may be related to their efficient metabolic transformation. Three ring PAHs dominated both in marine sediments and species, but low molecular weight PAHs exhibited higher proportions in biota than in sediments (p < 0.05). Petrogenic and pyrolytic sources both contributed to the occurrence of PAHs, and the latter became increasingly important in the study area. The ecological risk from PAHs in the sediments was relatively low (9% incidence of adverse biological effect) according to the effects-based sediment quality guideline values. Exposure to PAHs via consuming seafoods might pose a health risk to local residents. Overall, these results revealed anthropogenic activities in the coastal area have an impact on the local ecosystem.

Polycyclic aromatic hydrocarbons in surface waters and riverine sediments of the Hooghly and Brahmaputra Rivers in the Eastern and Northeastern India

Sixteen priority polycyclic aromatic hydrocarbons (PAHs) regulated by the United States Environmental Protection Agency (USEPA) were analyzed in surface waters and riverine sediments of Brahmaputra and Hooghly Rivers, along urban-suburban-rural transects. ∑16 PAHs concentrations were higher in Hooghly riverine sediment (HRS) (Avg, 445 ng g−1) than Brahmaputra riverine sediment (BRS) (Avg, 169 ng g−1) dominated by 4-ring PAHs. In contrast, PAHs concentrations in surface water of Brahmaputra River (BRW) (Avg, 4.04 μg L−1) were comparable with Hooghly River (HRW) (Avg, 4.8 μg L−1), with dominance by 3-ring PAHs. Toxic PAHs (BaA, Chr, BbF, BkF, BaP, InP and DBA) were dominant in sub-urban transect of HRS (Avg, 387 ng g−1) and BRS (Avg, 14 ng g−1). Diagnostic ratios, principal component analysis (PCA) and ring wise composition suggested combustion as the main PAHs source in these riverine belts. In BRS, higher PAHs in suburban and rural transects were attributed to incomplete combustion of fossil fuel and biomass burning. In HRS, >85% of high molecular weight PAHs were found in the industrial areas of the suburban transect possibly associated with the discharge of industrial effluents. Harbor and port activities were other major contributors of HMW-PAHs in Hooghly riverine system. Carcinogenic potency estimated in terms of toxic equivalent (TEQ) was several folds higher in HRS (Avg, 106 ng TEQ g−1) compared with BRS (Avg, 2.5 ng TEQ g−1). Mostly low molecular weight PAHs are likely posing a risk to fishes in both the rivers. Risk on edible fish species may be a matter of concern considering the regular consumption of fishes in this region.

Assessment of Pollution, Sources, and Risks of Polycyclic Aromatic Hydrocarbons in Soil from Urban Parks in Xi'an City, China

A total of seventeen surface soil samples were collected from urban parks in Xi'an city. The concentration of sixteen priority polycyclic aromatic hydrocarbons (PAHs) were analyzed by high performance liquid chromatography (HPLC). In addition, the composition, source, pollution level and a risk assessment of PAHs in surface soil of park were evaluated. The results showed that the total concentrations of sixteen PAHs ranged from 0.362 to 1.336 μg·g-1, with a mean value of 0.591 μg·g-1. The concentration of seven carcinogenic PAHs (Σ7CPAHs) ranged from 0.051 to 0.528 μg·g-1, with a mean value of 0.181 μg·g-1. Compared to the ΣPAHs levels of other cities of China, the ΣPAHs in park surface soils in Xi'an are relatively low. PAHs in the soil samples were dominated by low molecular weight PAHs with 2 and 3 rings. The results of source analysis showed that the PAHs in park surface soil mainly originated from the combustion of fossil fuels, however, the source of PAHs in some samples is complex and from mixed sources, such as oil spills, oil burning, and incomplete combustion of coal and biomass. The ecological risks of PAHs in the surface soil were evaluated according to the soil quality guidelines to be ERL (effects range low) and ERM (effects range median), and these results showed that all samples, in general, were polluted. However, the potential ecological risks of PAHs were at a low level. The incremental life cancer risk (ILCR) assessment indicated that health risks for children and adults were both in a permissible range, however, the risks for children exposed to the soil were considerably higher than for adults. Dermal contact was the main exposure pathway that resulted in the relatively higher risk, followed by ingestion.

The effect of multiple contamination of soil on LMW and MMW PAHs accumulation in the roots of Rubus fruticosus L. naturally growing near The Copper Mining and Smelting Complex Bor (East Serbia).

Samples of roots and spatial soils of native Rubus fruticosus L. were collected from the spots positioned at different distances from the copper smelter and city heating plants in the industrial zone of the town of Bor (Serbia) and subjected to chemical analyses in order to determine the content of several heavy metals, and 15 priority polycyclic aromatic hydrocarbons (PAHs). In this study, the results for 9 low and medium molecular weight PAHs (LMW and MMW PAHs) are represented and processed using the calculation of bio-concentration factors and statistical methods such as hierarchical cluster analysis and Pearson's correlation study with the aim of investigating the plant capabilities for their uptake from the soil and later accumulation into the root tissue, under the hostile circumstances of multiple contamination. The obtained data revealed different accumulation rates for the investigated PAHs and showed that in several cases, the contents of root PAHs were under the strong influence of present contaminants such as soil copper and some soil PAHs, indicating at the same time that R. fruticosus can regulate the processes of LMW and MMW PAHs extraction/accumulation using different mechanisms, depending on the existing environmental circumstances. The used mechanisms could be exploited in phytoremediation methods based not only on the extraction and concentration of PAHs in plant roots but also on PAH degradation or stabilization in the soil. Also, the results of this study confirmed that, except in the case of naphthalene and fluoranthene, there was no PAH pollution, which originated solely from the industrial zone.

Synergistic effects of engineered nanoparticles and organics released from laser printers using nano-enabled toners: potential health implications from exposures to the emitted organic aerosol.

Recent studies have shown that engineered nanoparticles (ENPs) are incorporated into toner powder used in printing equipment and released during their use. Thus, understanding the functional and structural composition and potential synergistic effects of this complex aerosol and released gaseous co-pollutants is critical in assessing their potential toxicological implications and risks. In this study, toner powder and PEPs were thoroughly examined for functional and molecular composition of the organic fraction and the concentration profile of 16 Environmental Protection Agency (EPA)-priority polycyclic aromatic hydrocarbons (PAH) using state of the art analytical methods. Results show significant differences in abundance of non-exchangeable organic hydrogen of toner powder and PEPs, with a stronger aromatic spectral signature in PEPs. Changes in structural composition of PEPs are indicative of radical additions and free-radical polymerization favored by catalytic reactions, resulting in formation of functionalized organic species. Particularly, accumulation of aromatic carbons with strong styrene-like molecular signatures on PEPs is associated with formation of semivolatile heavier aromatic species (i.e., PAHs). Further, the transformation of low molecular weight PAHs in the toner powder to high molecular weight PAHs in PEPs was documented and quantified. This may be a result of synergistic effects from catalytic metal/metal oxide ENPs incorporated into the toner and the presence/release of semi-volatile organic species (SVOCs). The presence of known carcinogenic PAHs on PEPs raises public health concerns and warrants further toxicological assessment.

Bioaccumulation and cancer risk of polycyclic aromatic hydrocarbons in leafy vegetables grown in soils within automobile repair complex and environ in Uyo, Nigeria.

Using gas chromatography-mass spectrometry and an incremental lifetime cancer risks (ILCRs) assessment model, the bioaccumulation and cancer risk of 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) in leafy vegetables (Vernonia amygdalina and Lasianthera africanum) grown in soils within an automobile repair complex environment in Uyo, Nigeria was studied. The total PAHs concentrations recorded for soils ranged from 0.02 to 1.77mg/kg. The highest level of 1.77mg/kg was recorded for soils from the main automobile repair complex (site 1). Low molecular weight (LMW) PAHs were predominant although some high molecular weight (HMW) PAHs suites (0.04mg/kg of chrysene and 0.04 of benzo[k]fluoranthene) were also found in site 1. The leafy vegetables accumulated PAHs were mostly LMW. Accumulation levels were similar but the extent of PAH uptake in vegetables was species dependent as V. amygdalina accumulated more (0.81mg/kg). The bioaccumulation factors (BaFs) calculated ranged from 0.22 to 0.63 for L. africanum, and 0.18 to 0.55 for V. amygdalina in site 1 where high PAH levels were recorded in soil. Pearson correlation coefficient analysis revealed a strong positive relation between the PAH content of soil and the amount accumulated by L. africanum (r=0.5) and V. amygdalina (r=0.8) at p=0.05. The vegetable's potential to bioaccumulate PAHs is indicative of their use as good bioindicators for PAH contamination in soil. Only two of the USEPA possible human carcinogenic PAHs were detected, and carcinogenic risk assessment based on occupational exposures to soil particles by adults revealed that the total risk level (7.17×10-5) contribution from incidental soil ingestion, dermal contact, and soil particle dust inhalation slightly exceed the USEPA acceptable limits (< 1.00×10-5). There is a need for public education on consumption of vegetables grown in and around automobile repair complexes across Nigeria.

Occurrence and Source Apportionment of Polycyclic Aromatic Hydrocarbons in Urban Residential Soils from National Capital Region, Uttar Pradesh, India

This study aims to investigate the level of priority polycyclic aromatic hydrocarbons (PAHs) and identification of their potential sources in residential soils. During the study, a total 36 soil samples collected from twelve residential locations at Sahibabad-Ghaziabad area of western Uttar Pradesh, India, a constituted part of the National Capital Region of India. Samples extracted using ultrasonication, cleaned with silica and analyzed by diode array detector–high-performance liquid chromatography using acetonitrile/water as mobile phase. The 25th and 75th percentile concentration of ∑PAHs was 264 μg kg−1 and 584 μg kg−1, respectively, with mean and median of 445 μg kg−1 and 421 μg kg−1. The detection frequency of PAHs in all samples was lower for low molecular weight PAHs (19%) than high molecular weight PAHs (81%). The concentration of seven probable carcinogenic PAHs accounted for 67% of the ∑PAHs. PAHs toxicity potential as benzo(a)pyrene toxicity equivalent ranged between 2.52–253 μg BaPTEQ kg−1. Composition profile of PAHs with different aromatic rings and selected diagnostic molecular ratios suggested the local pyrogenic sources of PAHs from vehicular emissions, diesel engines, biomass combustion, gasoline, and coal combustions.

Source contributions of Polycyclic Aromatic Hydrocarbons in soils around oilfield in the Brahmaputra Valley

Surface soils from Borholla oilfield in the upper Brahmaputra Valley in India were studied for the USEPA's 16 priority Polycyclic Aromatic Hydrocarbons (PAHs). Analysis of PAHs was carried out by high performance liquid chromatography (HPLC) system equipped with an UV detector. Seasonality in PAHs concentrations was evident and the concentrations were found to be greater in post-monsoon season. There has been a dominance of low molecular weight PAHs (80–90% of total PAHs) indicating recent deposition from combustion sources. The concentration profiles appeared in the decreasing order of 3-ring >2-ring >4-ring >5-ring >6 ring PAHs. The sources of PAHs were identified using isomer pair ratios and Principal Component Analysis-Multiple Linear Regression (PCA-MLR) and Positive Matrix Factorisation (PMF). The ratios of diagnostic pairs indicated for both pyrogenic and petrogenic input of PAHs. The PCA-MLR modelling revealed that the <16% of contribution came from petrogenic origin and the rest 85% was found to be from pyrogenic sources. The PMF model also shown that <19% of PAHs source were petrogenic origin whereas rest from pyrogenic origin. The correlations of black carbon (BC) with PAHs also supported the pyrogenic contribution. The analysis of air mass back trajectories revealed that there has been contribution of both local and distant sources, through long range transport of pollutants, which were deposited to the site.

Polycyclic aromatic hydrocarbon contamination in a highly vulnerable underground river system in Chongqing, Southwest China

The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were investigated in the water, sediment and topsoil of the Laolongdong underground river system (LURS) of Chongqing, Southwest China. The total concentrations of PAHs ranged from 81.5 to 8089ng/L in water, from 58.2 to 1070ng/g in sediment, and from 277 to 3301ng/g in topsoil. These levels of PAHs are relatively low compared to other karst areas. Low molecular weight (LMW) PAHs were dominant in water, sediment, topsoil samples, and high molecular weight (HMW) PAHs were more common in topsoil and sediment. The high levels of LMW PAHs in groundwater and sediment suggested relatively recent local sources of PAHs that were transported into the aquifer via wastewater discharge and surface water leakage. The similar composition of PAHs in topsoil and sediment samples suggested that the sediment originated from topsoil and that PAHs in sediment and topsoil had similar origins. The source of PAHs contamination was diagnosed by using PAH isomer ratios and a principal component analysis (PCA) method. The results indicated that PAHs mainly originated from vehicles, coal combustion and petrogenic sources. Significant correlations of PAHs with total organic carbon (TOC) in topsoil and sediment indicated that TOC was an important factor affecting PAHs content.

Environmental carcinogenic polycyclic aromatic hydrocarbons in soil from Himalayas, India: Implications for spatial distribution, sources apportionment and risk assessment

The Indian Himalayan Region (IHR) is one of the important mountain ecosystems among the global mountain system which support wide variety of flora, fauna, human communities and cultural diversities. Surface soil samples (n = 69) collected from IHR were analysed for 16 priority polycyclic aromatic hydrocarbons (PAH) listed by USEPA. The ∑16PAH concentration in surface soil ranged from 15.3 to 4762 ngg−1 (mean 458 ngg−1). The sum total of low molecular weight PAH (∑LMW-PAHs) (mean 74.0 ngg−1) were relatively lower than the high molecular weight PAH (∑HMW-PAHs) (mean 384 ngg−1). The concentration of eight carcinogenic PAHs (BaA, CHR, BbF, BkF, BaP, DahA, IcdP, BghiP) were detected high in mountain soil from IHR and ranged from 0.73 to 2729 ngg−1 (mean 272 ngg−1). Based on spatial distribution map, high concentration of HMW- and LMW-PAHs were detected at GS1 site in Guwahati (615 and 4071 ngg−1), and lowest concentration of HMW-PAHs were found at IS6 in Itanagar (5.80 ngg−1) and LMW-PAHs at DS2 (17.3 ngg−1) in Dibrugarh. Total organic carbon (TOC) in mountain soil was poorly connected with ∑PAHs (r2 = 0.072) and Car-PAHs (r2 = 0.048), suggesting the little role of TOC in adsorption of PAHs. Isomeric ratio of PAHs showed the source of PAH contamination in IHR is mixed of petrogenic and pyrogenic origin and was affirmed by PAHs composition profile. These source apportionment results were further confirmed by principal component analysis (PCA). Eco-toxicological analysis showed the calculated TEQ for most carcinogenic PAH were 2–4 times more than the Dutch allowed limit, while TEQ of BaP was 25 times high, suggesting increasing trend of carcinogenicity of surface soil.

Fly ash from coal combustion – An environmental source of organic compounds

The fly ash resulting from coal combustion (anthracite A coal type) for power generation was investigated. The fly ash produced during the coal combustion was emplaced in surface landfills near the thermal power plant facilities. A total of six samples were collected in the fly ash landfills which were therefore analyzed for their geochemical characterization. The analysis comprised the determination of total organic carbon and total sulfur, the identification of aliphatic hydrocarbons, and the identification and quantification of the sixteen priority polycyclic aromatic hydrocarbons (PAHs). This study provides information about the potential environmental impacts associated with the disposal of fly ash and, in addition, it also provides scientific knowledge about the effects of combustion process in the soluble fraction of coal organic matter and about the behavior of these compounds during combustion. The results about the aliphatic compounds demonstrated that the long-chain n-alkanes, the pentacyclic terpanes, and the regular steranes (C-27, C-28, C-29) increase in fly ash samples comparatively to coal. The PAHs with two and three aromatic rings (low molecular weight PAHs – LMW PAHs) were not detected in fly ash while fluoranthene (four rings) was detected in all samples, and benzo[a]anthracene (four rings), benzo[b]fluoranthene (four rings), indeno[123-cd]pyrene (five rings), benzo[ghi]perylene (five rings), and dibenzo[ah]anthracene (six rings) were detected in some of the samples. The absence of LMW PAHs and the presence of some high molecular weight (HMW) PAHs, with four to six rings, are attributed to the combustion process. The low sum of the priority PAHs in fly ash samples can be related with both, the high rank of the coal burned in the thermal power plant (anthracite A), with the technical combustion conditions and/or leaching process in the fly ash landfills. The organic compounds adsorbed in fly ash particles may be released into the environment and therefore can represent a potential source of contamination of soils and waters and human health problems.

Sources and distribution of polycyclic aromatic hydrocarbons of different glaciers over the Tibetan Plateau

Twenty snow samples were collected from the Qiyi glacier in Qilian Mountains, the Yuzhufeng glacier in eastern Kunlun Mountains, the Xiaodongkemadi glacier in Tanggula Mountains, and the Gurenhekou glacier in Nyainqentanglha Range over the Tibetan Plateau. The concentration and distribution features of sixteen priority Polycyclic Aromatic Hydrocarbons (PAHs) were determined by gas chromatography equipped with a mass spectrometry detector (GC-MS). The sources of these PAHs were explored as well. Our results indicated that the average concentrations of PAHs in snow were in the range of 20.45–60.57 ng/L. Maximum PAHs levels were found in the YZF glacier and minimum in the XDKMD glacier. However, no apparent regional distribution pattern of PAHs was found in the glaciers over the Tibetan Plateau. Moreover, the 2–4 ring low molecular weight PAHs predominated in snow samples and the concentrations of phenanthrene was the highest. Integrated factor analysis and isomer pair ratios suggested that PAHs of glaciers over the Tibetan Plateau were derived from low temperature combustion of coal and biomass, and partially from the exhaust gas of locomotives. Air mass back trajectory indicated that organic compounds detected in snowpit of these four glaciers, in the period of time they represented, mainly came from Central Asia and the arid area of Northwest China by westerly wind circulation.